Control system for load lifting apparatus



Oct. 24, 1967 R. A. NIEMINSYKI 3,348,635

CONTROL SYSTEM FOR LOAD LIFTING APPARATUS Filed Aug; 26, 1966 I 2 Sheets-Sheet 1 I ZZ 445 j l 56 J 2 I I 2 i l Zfi I if I I f I I I .9 a? I IE fif j! i -177 I r i1 F vii: lu/f5 Oct. 24, 1967 CONTROL SYSTEM FORLOAD LIFTING APPARATUS Filed Aug. 26, 1966 2 Sheets-Sheet 2 9% BATTERY0R POWER SUPPLY, ya F xvi RESERVOIR}.

- INVENTOR. Q- A7054??? 4. MEMl/VSK/ 7Z'A6A/0 & Toppy R. A. NIEMINSKI3,348,635

United States Patent Ofifice 3,348,635 Patented ea. 24, 1967 3,348,635CONTROL SYSTEM FOR LOAD LIFTING APPARATUS Robert A. Nieminski,Philadelphia, Pa., assignor to Eaton Yale & Towne Inc., Cleveland, Ohio,a corporation of Ohio Filed Aug. 26, 1966, Ser. No. 575,350 Claims. (Cl.187-9) The problem.

A stacker crane usually comprises a pair of vertically disposed primaryuprights mounted for lateral movement on a horizontal rail systemsupported near the ceiling. The upper ends of the primary uprights arepositioned near the ceiling rails and, accordingly, the lower endsthereof terminate a substantial distance above the floor in order not tointerfere with the movement of men and materials about the floor. A pairof secondary uprights is supported by the primary uprights. Thesecondary uprights are mounted on the primary uprights for verticalmovement so that the lower ends can be brought down to the floor levelfor the purpose of picking up and lifting a load, by means of a loadcarriage including a lift fork or the like.

A hydraulic ram can be utilized for moving the secondary uprightsrelative to the primary uprights to effect the load lifting operation.Thus, a primary ram extending between the primary and secondary uprightscontributes the movement of the sec-ondary uprights from an extremelowered position at the floor, to an extreme high position.

As indicated, a load carriage is mounted on the sec ondary uprights forvertical movement so that the load can be moved from the floor to thetops of the secondary uprights. By s-o operating, the load can be movedbetween the floor and ceiling for stacking purposes; the lateral railsystem provides lateral movement relative to the floor between one areaand another.

A hydraulic ram can be mounted between the load carriage and thesecondary uprights. This load or secondary ram contributes the movementof the load carriage relative to the secondary uprights from a fullylowered floor position to a fully elevated position relative to thesecondary uprights. Load carriage movement relative to the secondaryuprights can be brought about by direct thrust of the ram, or throughthe intermediary of chains or other means as those skilled in the artwill fully appreciate.

Thus, it may be said that my invention is particularly related to astacker crane in which a load carriage moves relative to secondaryuprights, and the secondary uprights and load carriage move togetherrelative to the primary uprights, a secondary ram contributing movementof the load carriage relative to the secondary uprights and a primaryram contributing movement of the secondary uprights and load carriagerelative to the primary uprights.

The principles enumerated above are equally applicable to a fork lifttruck which can be considered an inversion of a stacker crane. Thus, theprimary uprights of a fork lift truck are mounted for lateral movementover a floor on a wheeled vehicle. The secondary uprights are movablymounted on the primary uprights for first vertical lift movement, andthe load carriage is movably mounted on the secondary uprights forsecondary vertical lift movement. This is the converse arrangement ofthe stacker crane, but embodies the same principles of operation.

The problem arises in the operation of a stacker crane or a lift truckembodying primary and secondary lifting rams. Thus, it will beappreciated that two basic movements are involved in moving a load: (1)vertical movement in the picking up of a load; and, (2) lateral movementrelative to the floor after the load has been picked up and before it isset down again.

Heretofore, it has not been possible for the operator to laterally movethe crane while load lifting is in progress because his attention mustbe kept constantly fixed on the vertical lifting which involves thestrictly manual operation of the primary and secondary rams. Only afterthe lifting is completed, can he then remove his hands from theoperating buttons for the lift rams and then actuate the crane by meansof separate control buttons for lateral load movement.

Sequential lifting is not alleged to be new, per se, in the presentinvention. However, the particular system disclosed herein for providingsequential lifting is novel. Sequential lifting is presently obtained byrelying on variations in pressure between rams, because of differingloads. However, in the pressure variation sequential lifts, there is thepossibility that friction will cause lifting in a sequence that is notdesirable, and sometimes latches must be utilized to provide propersequencing. The present invention may be utilized as the basis forcontributing sequential lifting in stacker cranes and industrial lifttrucks while eliminating holding latches. Thus, a hydraulic circuit isprovided that will hold each ram that is not energized, so that duringthe period in which the particular ram is not energized, it functions tohold Whatever mechanism it controls.

From the foregoing, it will be evident that automatic and sequential, aswell as individual, operation of the lifting rams will contributesubstantially to the advancement of the stacker crane art. Thus,automatic sequential operation of the rams would permit the operator tostart the lifting and then proceed immediately with the lateral cranemovement while load lifting continues under automatic control. Operationwould be substantially expedited and efliciency and safety would beimproved.

Accordingly, it is an important object of this invention to improve theart of stacker cranes and analogous lifting devices by contributing amore effective and efiicient mechanism and means for controlling theoperation of the lifting rams.

My invention provides a substantial contribution to the operation of thestacker crane principle by providing both individual and automaticsequential operation of the lift rams. Thus, the control means or systemof this invention,

permits the individual operation of the load ram, as I call it,operating to lift the load carriage relative to the secondary uprights.Also, the control means of this invention permits individual operationof the main hydraulic ram, as I call it, operating to lift the carriageand secondary uprights together, relative to the primary uprights. Thus,should the operator desire to lift the load through movement first ofthe secondary uprights and load carriage relative to the primaryuprights, e.g., by actuating the main hydraulic ram, he need merelybring about the operation of the main hydraulic ram.

But, as a special feature of the invention, automatic sequentialoperation is also provided. Thus, upon completion of the full operationof the main hydraulic ram, the load ram will be automatically andsequentially operated to bring about the full movement of the loadcarriage relative to the secondary uprights. Because of this automaticsequential operation, the operator can start the lift operation andproceed immediately to maneuver the stacker crane laterally relative tothe fioor, once lie has set the main ram in operation, knowing full wellthat the load will be automatically lifted to and stopped at the maximumwithout further attention on his part.

Also, the automatic operation of the invention provides that if the loadram is actuated first, sequential operation of the primary ram willfollow. Thus, if the load ram is actuated first, upon completion of thefull operation of the load ram, the main ram will be automatically andsequentially operated to bring about the full movement of the load.Thus, if the load ram is first to receive hydraulic fiuid, it will movethe load carriage to an extreme elevated position relative to thesecondary uprights, after which the main ram will be automaticallyactuated to complete the full lifting movement by elevating thesecondary uprights and load carriage together on the primary uprights.In this situation, the operator can also proceed with lateral movementof the crane without further attention to the lifting operation, knowingthat it will terminate either when maximum lifting has been achieved, orwhen he removes his hand from the valve actuator button if he sodesires.

It is important to appreciate that this automatic sequential liftingwill be brought about without, in any way, interfering with theindividual operation of each ram, if such operation is desired.

A feature of the invention is that in moving the load downwardly, thetwo rams must be individually operated. The reason for this isbroughtout below.

I have thus outlined the general nature of my invention and its relationto the prior art in order that the description thereof that follows maybe better understood, and in order that my contributions to the art maybe better appreciated. There are, of course, additional features of myinvention that will be described hereinafter and which will form thesubject of the claims appended hereto. Those skilled in the art willappreciate that the conception on which my disclosure is based mayreadily be utilized as the basis for the designing of other structuresfor carrying out the reversal purposes of my invention. It is important,therefore, that the claims granted to me shall be construed sufficientlybroadly to prevent the appropriation of my invention by others skilledin the art.

Referring now to the drawings, FIGURE 1 is a vertical elevation showingschematically the arrangement of a stacker crane having the controlmeans of the invention applied thereto and including details such as theoperators compartment and the pump motor; FIGURE 2 is a top plan viewtaken as along the line 22 of FIGURE 1, but of an actual stacker crane,showing the arrangement of the operators compartment on the secondaryuprights, the pump and reservoir for hydraulic fluid, and the liftforks; and, FIGURE 3 is a hydraulic piping and flow diagram in schematicform, showing the flow control valves, forming part of the invention;the tilting cylinders and nonpertinent flow rate valves have not beenshown because it is not believed that they are necessary for theeffective showing and claiming of my invention; but the two manuallymovable valves are shown, but more broadly and without detail, sincetheir specific construction is not significant.

Referring now more particularly to the drawings, and more especially toFIGURE 1, a stacker crane is designated by the reference numeral 20. Amovable carriage 22 is supported for transverse movement relative to thefloor line 24, and is mounted on a horizontal rail system supported nearthe ceiling of a warehouse bay. Though not shown, because conventional,the rail system customarily comprises a pair of parallel longitudinalrails extending the length of the warehouse bay, with a large beamtransversely straddling the rails with wheels at each end operablyengaged with the rails. The beam carries a cross rail, or rails, and themovable carriage 22 operates on the cross rails. The combination railsets provide for lateral movement all over a given warehouse bay floorarea.

Supported from the movable carriage 22 is a pair of primary uprights 26.It will be evident that the upper ends of the primary uprights 26 arethereby positioned near the ceiling rails and, accordingly, the lowerends 28 terminate a substantial distance above the floor line 24 inorder not to interfere with the movement of men and materials about thefloor.

A pair of secondary uprights 30- is mounted for vertical movement on theprimary uprights 26. The movement is provided in part by wheels 31mounted to the secondary uprights by means of exemplary brackets 32. Thewheels 31 operate within channel tracks carried by the primary uprights26. By this arrangement, the lower ends 34 of the secondary uprights 30can be brought down to fioor level for the purposes of picking up andlifting a load, by means of a load carriage 36, including a lift fork38.

A primary hydraulic ram is utilized for moving the secondary uprights 30relative to the primary uprights 26 to effect the load liftingoperation. The upper end of the piston rod 42 of the primary ram 40 issecured to the bottom of the movable carriage 22 as by welding at 44.

A piston 46 is attached to the lower end of the piston rod 42 forreciprocation with the cylinder 48 of the primary ram 40. The piston rod42 operates through a head 50, containing a suitable packing, not shown,to provide a sliding seal relative to the piston rod as the primarycylinder 48 moves up and down the piston rod.

The lower end 52 of the primary cylinder is attached to, for the purposeof carrying, the base plate 54 by means of a weld 44. The base plate 54bridges and holds together the secondary uprights 30 in alignedrelationship. Incidentally, other cross-bridging, not shown, is usedacross the tops of the secondary uprights 30 to provide a rigidsecondary upright unit.

Thus, the primary ram 40, extending between the primary uprights 26 andthe secondary uprights 30, contributes the movement of the secondaryuprights from an extreme lowered position at the floor 24 to an extremehigh position. The extreme high position is achieved when the head ofthe primary cylinder 48 engages the primary or #1 limit switch 56.

The load carriage 36 is mounted on the secondary uprights 30 forvertical movement, so that the load can be moved from the floor line 24to the tops of the secondary uprights. The movement is provided, inpart, by wheels 58 mounted to the load carriage 36 by means of exemplarybrackets 60'. The wheels 58 operate within channel tracks, not shown,carried by the secondary uprights 30. By this arrangement the horizontaltines 62 of the lift fork 38 of the load carriage 36 can be brought downto the floor level 24 for the purpose of picking up and lifting theload. The load thus can be moved from floor to ceiling for stackingpurposes and the rail system provides lateral movement relative to thefloor between one storage area and another.

A secondary hydraulic ram 64 is utilized for moving the load carriage 36relative to the secondary uprights 30. Thus, the base 66 of the cylinder68 of the secondary ram 64 is attached to the upper surface of the baseplate 54 as by welding at 44. A piston 70 operates within the cylinder68 of the secondary ram 64 and is connected to a piston rod 72 whichextends out the top of the cylinder. The piston rod 72 operates througha head 74, containing a suitable packing, as described for the head 50of the cylinder 48 of the primary ram 40.

The exposed upper end of the piston rod 72 is attached to a pulleyhaving a suitable rotatable sheave 76, over which a lift chain 78 islapped. One end of the lift chain 78 is fastened to the secondaryupright 30 at the point 80. The other end of the lift chain 78 isfastened to the lift fork 38 at the point 82. The lift chain 78 ismaintained in an upwardly extending vertical bight. By this arrangement,movement of the piston rod 72 of the secondary ram 64 will act on thelift chain 7 8 to lift the load carriage 36 relative to the secondaryuprights 30, the rate of movement of the load carriage being twice thespeed of movement of the piston rod.

Thus, the load or secondary ram 64, extending between the secondaryuprights 30 and the load carriage 36, contributes the movement of theload carriage relative to the secondary uprights from a fully loweredfloor position 24, to a fully elevated position relative to thesecondary uprightsrThe fully elevated position is achieved when thesheave 76, carried by the secondary ram piston 72 engages the secondaryor #2 limit switch 90.

It should also be noted that an operators compartment 84 is mounted onthe secondary uprights 30, outboard of, but adjacent to the secondaryuprights and directly behind the load carriage 36. By this arrangement,the operator is provided with a clear view of the horizontal tines 62for picking up and laterally moving a load. Along with the operatorscompartment 84, the secondary uprights 30, at the base end, also carry apump motor 86, for a pump, hidden behind a reservoir 88 for hydraulicfluid, all as shown more particularly in FIGURE 2 of the drawings.

Having explained the manner in which my invention is related to astacker crane, I will now proceed to describe fully and in detail thespecific aspects of the invention.

By reference more particularly to FIGURE 3 of the drawings it will beobserved that the primary ram 40 receives pressurized fluid undercontrol of a -manually operated primary up-down valve '92. The valve 92is connected to a supply line 94 that in turn is connected to to thepump 96, driven by motor 86. Pump 96 receives strained hydraulic fluidfrom the reservoir 88. The primary up-down valve 92 is also connected bymeans of a line 98 to the reservoir 88 for the purpose of dumping theprimary-ram 40 during a lowering operation, to be described later. Theother side of the primary up-down valve 92 is connected to a line 100that leads to the top of the cylinder 48 of the primary ram 40 forraising the cylinder as indicated in dotted outline in FIG- URE 3, andalso in FIGURE 1.

The secondary hydraulic ram 64, for lifting the load carriage 36relative to the secondary uprights 30, receives hydraulic fluid underpressure and under control of manually operated secondary up-down valve102. The valve 102 is also connected to the supply line 94; and by meansof a line 98 is connected to the reservoir 88 for dumping the secondaryram 64 during a lowering operation, to be later described. The otherside of the secondary up-down valve 102 is connected to a line 104 thatleads to the bottom of the cylinder 68 of the secondary ram 64, beingconnected in beneath the piston 70 to push up the piston rod 72, asindicated in dotted outline, and as also described relative to FIGURE 1.

There are two automatic sequence control valves in the left system; one,the primary, being designated by the reference numeral 106; and theother, the secondary, being designated by the reference numeral 108. Theprimary automatic sequence control valve 106 provides one-way flow fromthe line 100 to the line 104. The one-way check valve element 110assures the oneway flow. The primary automatic sequence valve 106 isnormally closed, but a solenoid 112, which is adapted to be actuated bythe #1 or primary limit switch 56 being engaged by the cylinder 48 ofthe primary ram 40, is used for the purpose of opening the valve.

The secondary automatic sequence control valve 108 is also a one-wayunit, providing one-way flow from the line 104 to the line 100. Theone-way check valve element 114 assures the one-way flow. The secondaryautomatic sequence valve 108 is also normally closed, but a solenoid116, which is adapted to be actuated by the #2 or secondary limit switch90 being engaged by the piston rod 72 of the secondary ram 64, is usedfor the purpose of opening the valve.

The electrical control circuit includes a battery or power supply 118,having one side connected to a line 120 which leads to each of the limitswitches and 56. The limit switch 56 is in turn connected by means ofline 122 to the solenoid 112 of the primary automatic sequence controlvalve 106. The limit switch 90 is in turn connected via line 124 to thesolenoid 116 of the secondary automatic sequence control valve 108. Theother sides of each solenoid 116 and 112 are connected to the other sideof the power supply 118 by means of line 126.

In summary, both automatic sequence control valves 106 and 108 arenormally closed, thereby preventing flow between lines and 104 in eitherdirection. However, the valves 106 and 108 are adapted for opening bysolenoids 112 and 116, in turn energized by the limit switches 56 and90, respectively, under control of primary ram 40 and secondary ram 64.

The present description relates particularly to the load liftingoperation. The lowering of the rams will be discussed at the end of thislifting description.

When the up button 128 of the manual primary updown valve 92 is pressedby the operator, e.g., to be moved to the right from its position inFIGURE 2, pressurized hydraulic fluid will flow through the line 100into the primary ram 40, above the piston 46, to force the primarycylinder 48 to rise. This action is effective to elevate the secondaryuprights 30, FIGURE 1, relative to the primary uprights 26. It will benoted that hydraulic fluid cannot flow from line 100 through thesecondary automatic sequence control valve 108 to line 104 to causelifting of the secondary ram 64, because of the check valve element 114.Fluid can flow, however, from line 100 to line 104 through the primaryautomatic sequence control valve 106, but will not, since that valve isnormally closed. However, as soon as the secondary uprights 30, FIGURE1, have been raised to a fully lifted position by the primary ram 40,engagement of the cylinder 48 of the primary ram with the limit switch56 will excite the solenoid 112 to open the valve 106. This stopsfurther lifting of the primary ram 40. With the valve 106 opened, fluidwill then flow from the line 100 to the line 104 and thence to thesecondary ram 64. This will bring about the up movement of the pistonrod 72 of the secondary ram to lift the load carriage 36 and the liftfork 38, FIGURE 1, relative to the secondary uprights 30.

Should the up button 130 of the manual secondary up-down valve 102 bepressed by the operator, e.g., to be moved to the right from itsposition in FIGURE 3, rather than manual valve 92, the secondary ram 64will be the first to be actuated. Thus, fluid will flow through line 104into the secondary ram 64 beneath the piston 70 to force the piston andthe piston rod 72 to rise. Relative to FIGURE 1, this action iseffective to elevate the load carriage 36 relative to the secondaryuprights 30. It will be noted that hydraulic fluid cannot flow from line104 through the primary automatic sequence control valve 106 into line100 because of the check valve element 110, under any circumstances.Fluid can flow, however, from line 104 into line 100 through secondaryautomatic sequence control valve 108, but will not since the valve isnormally closed. However, as soon as the load carriage 36 has beenraised to a fully lifted position by the piston rod 72 of the secondaryram 64, engagement of the upper end of the piston rod with the #2 orsecondary limit switch 90 will excite the solenoid 116 to open the valve108. This.

stops further lifting by the secondary ram 64. With the valve 108opened, fluid will then flow from line 104 through secondary automaticsequence valve 108 into line 100 and into the primary ram 40. This willbring about the automatic sequential up movement of the cylinder 48 ofthe primary ram 40 to lift the secondary uprights 30 and the loadcarriage 36 together relative to the primary uprights 26.

From the foregoing, it will be appreciated that either the primary ram40 or the secondary ram 64 can be actuated first and sequencing of theother ram will automatically follow.

It will also be appreciated that at all times either of the rams 40 or64 can be operated to lift, or lower, individually, without in any waybringing about movement of the other ram, provided the limit switches 56and 90 are not brought into play.

Also, if one of the limit switches 56 and 90 is brought into play, afterfull extension of one of the rams 40 or 64, the other ram can becontrolled to lift by either one of the manual up-down valves 92 or 102.

Lowering is effected manually because once the limit switches 56 and 90have been opened the sequence valves 106 and 108 are automaticallyclosed. Thus, lowering of the primary ram 40 and the secondary ram 64 iseffected individually. To lower the primary ram 40, the down button 132of the manual primary up-down valve 92 is pressed by the operator, e.g.,to be moved to the left from its position in FIGURE 3. This causes fluidfrom line 100 and the primary ram 40 to dump through line 98 into thereservoir 88. To lower the secondary ram 64, the down button 134 of themanual secondary updown valve 102 is pressed by the operator, e.g., tobe moved to the left from its position in FIGURE 3; this causes fluidfrom line 104 and secondary ram 64 to dump through line 98 to reservoir88.

No sequential movement is possible for the lowering operation.Sequential movement is not desirable during a lowering operation becauseof the danger that the load might move, without direct supervision ofthe operator, into a position to create danger or to injure personnel.

I believe that the considerable merits and the great simplicity of myinvention will now be understood and appreciated by those skilled in theart.

I claim:

1. In a combination of the class described, a fluid pressure sourcehaving a high pressure side and a low pressure side, a primary uprightextending from a base, a secondary upright movably mounted on saidprimary upright, a load carriage movably mounted on said secondaryupright, a main hydraulic ram operable between said primary upright andsaid secondary upright for moving said secondary upright relatively tosaid primary upright, a second hydraulic ram operable between saidsecondary upright and said load carriage for moving said load carriagerelatively to said secondary upright, operating valve means for saidrams, the movement of said operating valve means to particular liftpositions directing fluid from the high pressure side of said pressuresource to one of said rams while the other ram remains inoperative,control valve means for said rams, and means whereby the operation ofeither of said rams to a particular extended position actuates saidcontrol valve means to effect the movement of fluid to the other ramduring positioning of said operating valve in lift position so that thetwo rams operate automatically in sequence regardless of which ram isfirst energized.

2. In the combination of claim 1, the feature that said control valvemeans comprise two valves with one or the other of said valves actuatedrespectively by the movement of one or the other of said rams to anextended position.

3. In the combination of claim 1, the feature that said control valvemeans comprises two one-way solenoid valves, with one of said valvesbeing actuated respectively by the movement of one of said rams to anextended position to actuate the solenoid of said one valve, and withthe other of said valves being actuated respectively by the movement ofthe other of said rams to an extended position to actuate the solenoidof said other valve.

4. In the combination of claim 1, the feature that there are two manualoperating valves comprising said operating valve means, one for eachram.

5. In the combination of claim 4, the feature that said other ram may becontrolled to lift by either operating valve once one of said rams hasbeen extended.

6. In the combination of claim 5, the feature that each of saidoperating valves controls lowering of the load by its ram through flowof fluid from its ram through the operating valve to the low pressureside of said fluid pressure source.

7. In the combination of claim 5, the feature that each of said ramslowers the load through movement of fluid therefrom through itsoperating valve.

8. In a combination of the class described, a fluid pressure sourcehaving a high pressure side and a low pressure side, a primary uprightextending vertically from a base, a secondary upright movably mounted onsaid primary upright, a load carriage movably mounted on said secondaryupright, a main hydraulic ram operable between said primary upright andsaid secondary upright for moving said secondary upright relatively tosaid primary upright, a second hydraulic ram operable between saidsecondary upright, and said load carriage operable to lift said loadcarriage relatively to said secondary upright, an operating valve forsaid main ram and an operating valve for said second ram, each of saidvalves communicating with its ram through a passage for hydraulic fluid,the movement of one of said valves to a lift position directing fluidfrom the high pressure side of said pressure source to one of said ramswhile the other ram remains inoperative, a control valve for each ofsaid rams, said valves being in reverse, parallel arrangement betweenthe said passages for hydraulic fluid, and means whereby the operationof either of said rams to a particular extended position actuates one ofsaid control valves to effect the movement of fluid therethrough to thepassage connecting the other operating valve with the other ram so thatthe two rams operate automatically in sequence regardless of which ramfirst receives fluid.

9. In the combination of claim 8, the feature that each control valvecomprises a one-Way solenoid valve, with one of said solenoid valvesbeing actuated respectively by movement of one of said rams to anextended position to actuate the solenoid of said one valve, and withthe other of said solenoid valves being actuated respectively bymovement of the other of said rams to an extended position to actuatethe solenoid of said other valve.

10. In the combination of claim 8, the feature that said other ram maybe controlled to lift by either operating valve once one of said ramshas been extended.

11. In the combination of claim 8, the feature that each of said ramslowers the load through movement of fluid therefrom through itsoperating valve.

12. In the combination of claim 8, the feature that each of saidoperating valves controls lowering of the load by its ram through flowof hydraulic fluid from its ram through the said operating valve to thelow pressure side of said fluid pressure source.

13. In a combination of the class described, a fluid pressure source, amain hydraulic lifting ram, a second hydraulic lifting ram, operatingvalve means for said rams, the movement of said operating valve means toparticular lift positions directing fluid to one of said rams while theother ram remains inoperative, control valve means for said rams, andmeans whereby the operation of either of said rams to a particularextended position actuates said control valve means to effect themovement of fluid from said pressure source to the other ram duringpositioning of said operating valve in lift position so that the tworams operate automatically in sequence regardless of which ram is firstenergized.

14. In a stacker crane having a carriage mounted for lateral movement ona horizontal rail system,

a vertically disposed primary upright having the upper end secured tosaid movable carriage,

a vertically disposed secondary upright mounted for vertical movement onsaid primary upright,

a primary ram having one operating portion secured to said movablecarriage and the other operating portion secured to said secondaryupright for movement of said secondary upright relative to said primaryupright upon application of pressurized hydraulic fluid into saidprimary ram,

said secondary upright having a load carriage vertically movablethereon,

a secondary ram having one operating portion secured to said secondaryupright and the other operating portion engageable to move said loadcarriage relative to said secondary upright upon application ofpressurized hydraulic fluid into said secondary ram,

first limit switch means on said primary upright and second limit switchmeans on said secondary upright,

a source of pressurized hydraulic fluid having a high pressure side anda low pressure side,

first manually operated valve means connected to supply pressurizedfluid from said high pressure side through a first passage to saidprimary ram and second manually operated valve means connected to supplypressurized fluid from said high pressure side through a second passageto said secondary ram,

first and second control valve means connected in reverse parallel fl-owrelation between said first and second passages,

and connection means between said first and second control valve meansand said first and second limit switch means, respectively.

15. The invention of claim 14 wherein the first control valve means, onactuation, provides flow only from said first to said second passagemeans, and wherein the second control valve means, on actuation,provides flow only from said second to said first passage means.

References Cited UNITED STATES PATENTS 2,607,197 8/1952 Johnson 911893,027,876 4/1962 Strick 91189 FOREIGN PATENTS I 1,068,627 11/ 1959Germany.

EVON C. BLUNK, Primary Examiner. H. C. HORNSBY, Assistant Examiner.

1. IN A COMBINATION OF THE CLASS DESCRIBED, A FLUID PRESSURE SOURCEHAVING A HIGH PRESSURE SIDE AND A LOW PRESSURE SIDE, A PRIMARY UPRIGHTEXTENDING FROM A BASE, A SECONDARY UPRIGHT MOVABLY MOUNTED ON SAIDPRIMARY UPRIGHT, A LOAD CARRIAGE MOVABLY MOUNTED ON SAID SECONDARYUPRIGHT, A MAIN HYDRAULIC RAM OPERABLE BETWEEN SAID PRIMARY UPRIGHT ANDSAID SECONDARY UPRIGHT FOR MOVING SAID SECONDARY UPRIGHT RELATIVELY TOSAID PRIMARY UPRIGHT, A SECOND HYDRAULIC RAM OPERABLE BETWEEN SAIDSECONDARY UPRIGHT AND SAID LOAD CARRIAGE FOR MOVING SAID LOAD CARRIAGERELATIVELY TO SAID SECONDARY UPRIGHT, OPERATING VALVE MEANS FOR SAIDRAMS, THE MOVEMENT OF SAID OPERATING VALVE MEANS TO PARTICULAR LIFTPOSITIONS DIRECTING FLUID FROM THE HIGH PRESSURE SIDE OF SAID PRESSURESOURCE TO ONE OF SAID RAMS WHILE THE OTHER RAM REMAINS INOPERATIVE,CONTROL VALVE MEANS FOR SAID RAM, AND MEANS WHEREBY THE OPERATION OFEITHER OF SAID RAMS TO A PARTICULAR EXTENDED POSITION ACTUATES SAIDCONTROL VALVE MEANS TO EFFECT THE MOVEMENT OF FLUID TO THE OTHER RAMDURING POSITIONING OF SAID OPERATING VALVE IN LIFT POSITION SO THAT THETWO RAMS OPERATE AUTOMATICALLY IN SEQUENCE REGARDLESS OF WHICH RAM ISFIRST ENERGIZED.